1. Technical Field
Embodiments of this disclosure relate to superabsorbents, also known as superabsorbent polymers or SAP, for the absorption of a broad spectrum of organic liquids at low percentages of absorber (5% or less). Specifically, the disclosure describes branched amide polymeric superabsorbents for the mitigation of hazardous organic solvents in the environment.
2. Discussion of the Prior Art
Current commercially available sorbents may require 10% (w/w) or more of material to immobilize organic liquids. They may also have a limited range of liquids for which they are highly effective. Generally, sorbents fall into two classes, i.e., adsorbents and absorbents. Adsorbents immobilize liquids through interaction of the liquid with the surface of the material and therefore have a capacity that can be limited by the material's surface area. Absorbents may also take liquid into the internal molecular structure of the material, resulting in much higher capacity relative to adsorbents.
The balance of the interstitial solvent-material interactions and the absorption induced strain in the material determines the capacity of an absorbent material for a given solvent. The degree of swelling of a polymeric absorbent is solvent dependent, and depends on the chemical structure of the polymer backbone in addition to other factors.
Very few highly absorbent polymers for organic liquids and solvents have been identified in the literature; nearly all of them are based on alkyl acrylates. The alkyl acrylates strongly absorb some non-polar solvents but are unsuitable for solvents of higher polarity. A copolymer of alkyl acrylates with a hydrophobic trialkylammonium salt showed inverse behavior with a high absorption capacity for polar solvents and a low absorption capacity for nonpolar solvents. While the absorption capacity of the copolymer may be impressive (over one-hundred times its weight for some solvents), the material suffers from a very high projected manufacturing cost. None of the known absorbents have high absorption capacities over a broad range of solvent polarities and types, i.e., alkyl, aromatic, non-polar, polar aprotic, polar protic, etc.